Kearsney College Physics (Paper 1) Trial Exam August 2011 Page 1 of 13

KEARSNEY COLLEGE

(200 marks; 3 hours) Examiner: Mr Thompson Moderator: Mr Moerdyk This question paper consists of 12 pages and a graph sheet (page 13) for question 6.4 and 7.6 PLEASE READ THE FOLLOWING INSTRUCTIONS CAREFULLY 1. Please make sure that your question paper is complete.

2. Write your name on your answer sheet (graph paper) and the question paper.

3. Answer ALL the questions on the A4 paper provided

4. START EACH QUESTION AT THE TOP OF A NEW PAGE.

5. Use the data sheet whenever necessary.

6. Read the questions carefully.

7. It is in your own interest to write legibly and to set your work out neatly.

8. Show your working in all calculations.

9. Units need not be included in the working of calculations, but appropriate units should be shown in the answer.

10. Non-programmable calculators may be used.

11. Appropriate mathematical instruments may be used.

12. Number the answers correctly according to the numbering system used in this question paper.

Learning outcomes and levels of difficulty

LO1 LO2 LO3 Level 1 Level 2 Level 3 Level 4 TOTAL % 16 77 7 17 44 27 13

TARGET % 20 70 10 15 45 25 15

GRADE 12

PHYSICAL SCIENCES: PHYSICS Paper 1

TRIALS AUGUST 2011

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Kearsney College Physics (Paper 1) Trial Exam August 2011 Page 2 of 13 Question 1 – Multiple Choice Select the answer that you consider to be the most correct and place a cross (X) over the letter representing your choice, on the answer sheet on the inside front cover of your answer booklet. 1.1 The graph below represents the motion of a ball thrown vertically upwards from the top of a building. Which statement below best explains the motion of the ball? A constant decreasing velocity downwards B constant acceleration upwards C constant increasing velocity upwards D constant acceleration downwards 1.2 The graph below represents the change in force with time for a tennis ball that is struck by a

player. The area under the graph would give the; A change in kinetic energy of the tennis ball B work done on the tennis ball C change in momentum of the tennis ball D power of the tennis ball 1.3 A capacitor has a rating of 2200 µF. The quantity of charge which the capacitor can store at a potential difference of 40 V is; A 0,088 C B 88000 C C 55 C D 88 C

0

150

Force N

0,05 0,1 t/s

v m.s-1 t/s

+10

0

- 60

7 1

Kearsney College Physics (Paper 1) Trial Exam August 2011 Page 3 of 13 Questions 1.4 and 1.5 involve the electromagnetic spectrum as shown below.

Radio Waves Microwaves

Visible Light Ultraviolet X-Rays Gamma

Rays 1.4 Which part of the electromagnetic spectrum has been used to benefit mankind by improving

communication by means of mobile phones? A X-rays B Ultra Violet

C Gamma Rays D Microwaves

1.5 As the wavelength of the electromagnetic radiation decreases how does the frequency and

energy change? [5 x 2 marks = 10]

Frequency Energy

A Increases Increases

B Decreases Increases

C Decreases Decreases

D Increases Decreases

Red Violet

Infrared

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Kearsney College Physics (Paper 1) Trial Exam August 2011 Page 4 of 13 Question 2 Tour de France (Start this question at the top of a new page.) Andy Schleck rides along a flat road at the top of a hill that has a vertical height of 100 m, as shown in the diagram. He stops pedalling as he reaches point A, but continues moving with a constant velocity of 9 m.s-1 and free-wheels down the hill to point B. The total mass of Andy and his bike is 64 kg.

2.1 Convert 9 m.s-1 to km.h-1. (2)

2.2 Andy had to do work to summit the hill. Give the definition for work. (2)

2.3 Calculate the total mechanical energy of rider and bike at the top of the hill (position A). (6)

2.4 Andy loses 50 000 J of energy on the way down the hill, due to work done against friction. Calculate his speed as he reaches the bottom of the hill (position B). (4)

2.5 State the Law of Conservation of Momentum. (2)

2.6 Whilst moving at 20 m.s-1 Andy collides with a stationary spectator (mass 45 kg) at position C. The spectator is thrown forwards at 15 m.s-1. Calculate Andy’s speed immediately after the collision. Assume that the collision is linear. (5)

2.7 If the collision took place over a 0,6 s time period, calculate the force exerted by Andy on the spectator. (5)

2.8 On a new bike, Andy continues to ride at 8 m.s-1 in an Easterly direction, relative to the road. An ambulance races towards him on the opposite side of the road at 30 m.s-1 West, relative to the road. What is the velocity of Andy relative to the ambulance? (2)

2.9 Recently accidents involving cyclists have become common news in KZN. State TWO ways

in which the traffic authorities could change local road rules to accommodate cyclists on the road. (4)

[32]

100 m

B C

A

9 m.s-1

Kearsney College Physics (Paper 1) Trial Exam August 2011 Page 5 of 13 Question 3 Rubber Ball (Start this question at the top of a new page.) A rubber ball, with mass 20 g, is projected vertically upwards from the ground at an initial velocity of 20 m.s-1. It reaches its maximum height after 2 s. On its way down it lands on top of a small building and bounces. The velocity versus time graph below indicates the motion of the ball for a certain period of time. Ignore the effects of air friction. 3.1 Name the physical quantity that the magnitude of the gradient of this graph represents. (1)

3.2 Determine from the graph how many times the ball bounces. (1)

3.3 Prove that the time ‘X’ is 3,1 s. (3)

3.4 Use values from the graph to determine the height of the building. (4)

3.5 Calculate the change in momentum of the rubber ball during its first bounce. (5)

3.6 Was the collision with the ground during the first bounce elastic? Briefly explain your answer. (3)

[17]

Building

-20

0

7

11

- 7

-20

v (m.s-1)

X 2 3,8 4,5 t(s)

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Kearsney College Physics (Paper 1) Trial Exam August 2011 Page 6 of 13 Question 4 Olympic Opening (Start this question at the top of a new page.) At the Beijing Olympics in 2008 the Olympic flame was lit by an archer who fired an arrow up to the funnel that was to hold the flame for the duration of the tournament.

The archer stood 120 m from the base of the funnel and fired the arrow with an initial velocity of 46 m.s-1 at an angle of 55o to the horizontal. IGNORE frictional forces. 4.1 Calculate the maximum height reached by the arrow above the archer. (5) 4.2 Calculate the height of the funnel above the archer, if the arrow lands in the funnel as shown in the diagram. (8)

[13] Question 5 Boys Jumping (Start this question at the top of a new page.) Two boys with the same mass jump to the ground from the same window. A bends his knees when he touches the ground, while B keeps his knees as rigid as possible.

Answer each of the questions that follow.

Justify your answer in each case by providing a suitable explanation that makes reference to one or more suitable formulae.

5.1 Can a body possess momentum without possessing mechanical energy? (3)

5.2 Can a body possess mechanical energy without it possessing momentum? (3)

5.3 Do the boys experience the same change in momentum when they touch the ground? (3)

5.4 How does the force exerted by the ground on each boy, compare? (4)

Adapted from Study & Master Physical Science 2005 [13]

120 m

Height of funnel above archer

55o

46 m.s-1

Kearsney College Physics (Paper 1) Trial Exam August 2011 Page 7 of 13 Question 6 Pressure fuelled rocket (Start this question at the top of a new page.) Dylan investigates how increasing the air-pressure in a home-made rocket affects the maximum height reached. He uses a pump to change the pressure in his rocket. He fires the rocket vertically upwards each time.

6.1 Identify the following variables;

6.1.1 Independent

6.1.2 Dependent

6.1.3 ONE fixed variable (3)

He obtains the following results from his experiment.

Height (m) Pressure

(kPa) Reading 1 Reading 2 Reading 3 Average

150 3,8 4,2 4,0 4,0

160 4,8 5,2 5,3 5,1

170 6,9 5,6 6,4 6,3

180 7,2 7,9 7,7 7,6

190 9,0 8,6 8,8 ?

6.2 Calculate the average height for the three readings taken at 190 kPa. (1)

6.3 For which pressure are the readings the least precise? Explain your answer. (3)

6.4 On the answer sheet draw a graph to represent the relationship between the pressure and the average height achieved. (6)

6.5 What is the minimum pressure required before the rocket lifts off the ground? (2)

6.6 Draw labelled free-body diagrams to represent the forces acting on the rocket at each of the following stages in its flight;

6.6.1 immediately after it leaves the ground

6.6.2 as it reaches its highest point (5)

6.7 Draw a displacement - time sketch graph to represent the motion of the rocket from lift off until the rocket returns to the ground. Take up as the positive direction. Use the ground as the frame of reference. (3)

[23]

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Kearsney College Physics (Paper 1) Trial Exam August 2011 Page 8 of 13 Question 7 Generator (Start this question at the top of a new page.) The diagram below depicts a section of a highly simplified generator. These generators are used at electrical power stations to produce the electricity to be distributed across the national grid. 7.1 Name the parts of the generator that are labelled X. (1) 7.2 Give the function of the parts labelled X. (1) 7.3 Name the law that states the relationship between the induced emf and the rate of change of

magnetic flux linkage in the coil. (Do NOT state the law.) (2) 7.4 Name the law that can be used to determine the direction of the induced current in the coil. (Do NOT state the law.) (2) 7.5 The coil is rotated in a clockwise direction. In which direction will the current flow through the

coil when it is in the position shown in the diagram? State either ABCD or DCBA. (1) 7.6 It takes 0,01 ms to rotate the coil through 90˚.The maximum induced emf is 50 V. On the grid

provided on your ANSWER SHEET sketch a graph of induced emf vs. time for 0,08 ms of this generator’s operation, beginning with the position given in the diagram at time = 0. (5)

7.7 Consider the diagram showing the transmission of electrical power over long distances.

7.7.1 What type of transformer is represented by the letter A? (1)

7.7.2 What type of transformer is represented by the letter B? (1)

7.7.3 EXPLAIN why the transformers at A and B are needed. (4)

A B

S

X

N

Kearsney College Physics (Paper 1) Trial Exam August 2011 Page 9 of 13 7.8 The output of an a.c. generator can be rectified into d.c. by using a circuit such as that pictured

below. 7.8.1 Give the name of the circuit components labelled 1 to 4. (1) 7.8.2 Describe how these components (1 to 4) change alternating current (a.c.) to

direct current (d.c.). Refer to the direction of current flow through the diodes and the load in the above circuit. (4)

7.8.3 Draw a current versus time sketch graph to show the current through the load YZ.

(2) [24]

Question 8 Electric Circuit (Start this question at the top of a new page.)

In the circuit shown below the resistance of the connecting wires, ammeter and switch can be ignored. The voltmeters have a very high resistance and the battery has significant internal resistance. When the switch S is open the voltmeter V1 reads 9 V. When the switch is closed the ammeter reads 600 mA.

The switch, S, is now closed. 8.1 Calculate the total resistance in the external circuit. (3) 8.2 Calculate the internal resistance of the battery. (4) 8.3 Calculate the reading on the voltmeter V1. (3) 8.4 Explain why the voltmeter reading changes when the switch is closed. (2) 8.5 The 4 Ω resistor is replaced with a 4 W light bulb. V2 now reads 2 V.

8.5.1 Calculate the new reading on the ammeter. (4)

8.5.2 Explain why the reading on the voltmeter V1 decreases when the 4 Ω resistor is replaced with the 4 W bulb. (3) 8.6 The 4 W bulb used in the above circuit is a small filament bulb that is often found in old torches.

In newer torches filament bulbs are being replaced by LEDs.

Give THREE advantages that LED’s have over filament bulbs when used in torches. (6) [25]

•

600 mA

A

4Ω

•

•

• S

6Ω •

V1 V2

6Ω

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W

1 2

3 4

AC input from generator

DC output to load X

Y

Z

•

• •

•

•

Kearsney College Physics (Paper 1) Trial Exam August 2011 Page 10 of 13 Question 9 Sound experiment (Start this question at the top of a new page.) Michael collects data to investigate how the velocity of a sound source travelling TOWARDS a stationary listener affects the apparent frequency of the note heard by the listener. His hypothesis is: The faster a sound source moves towards the listener, the lower the frequency of the sound a stationary listener hears.

He plots his data on the graph below.

How the velocity of a sound source (vs) affects the apparent frequency of the sound heard by a stationary Listener (fL)

9.1 Name the following variables in the experiment; 9.1.1 independent 9.1.2 dependent 9.1.3 controlled (ONE only) (3) 9.2 Name the effect on which this experiment is based. (2) 9.3 What is the true frequency of the sound source when it is not moving? (2) 9.4 What is the apparent frequency of the sound the listener hears when the source moves at 20 m.s-1? (2) 9.5 Use your answers to questions 9.3 and 9.4 to calculate the speed of sound in air at the location where the experiment was conducted. (4) 9.6 Does the data Michael collect suggest that he can reject or accept his hypothesis? Justify your decision. (3) 9.7 Briefly explain how the graph would change if the source was moving AWAY from the observer. (2)

700

750

800

850

900

950

1000

Freq

uenc

y he

ard

by li

sten

er (

f L)

(Hz)

0 5 10 15 20 45 25 30 35 40

Velocity of sound source (vs) (m.s-1)

Kearsney College Physics (Paper 1) Trial Exam August 2011 Page 11 of 13 9.8 While attending the Virginia Air Show, Michael was impressed with the speed of the SAAF Hawk

Jets. Their maximum speed was 285 m.s-1. 9.8.1 Give the definition of Mach number. (2) 9.8.2 Calculate the Mach number for the Hawk jet if the speed of sound through air is 315 m.s-1, at high altitude. (2) 9.8.3 Define wavefront. (2) 9.8.4 Describe what is happening to the wavefronts in front and behind the jet as it travels at its maximum speed. A diagram to help illustrate your answer is required. Clearly show the direction in which the jet is travelling. (3) [27]

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Kearsney College Physics (Paper 1) Trial Exam August 2011 Page 12 of 13 Question 10 Photoelectric Effect (Start this question at the top of a new page.) The apparatus shown below was used to investigate the photoelectric effect. The apparatus allows for the investigation of several variables. The frequency and intensity of the incident radiation can be changed; the type of metal used and the emf supplied across the electrodes can be adjusted. 10.1 Early investigators of this effect found that a zinc plate, when negatively charged, would lose its charge when exposed to ultraviolet light, while a positively charged zinc plate showed no such effect. What could the investigators conclude from these observations? (2) 10.2 A source of bright red light and a source of faint blue light are shone in turn onto the metal surface for the same length of time. In both cases, electrons are ejected from the metal surface. 10.2.1 The wavelength of blue light is 440 nm. Calculate the energy of a photon from this source. Give your answer in eV. (5) 10.2.2 Define threshold frequency. (2) 10.2.3 The maximum kinetic energy of the electrons ejected by the faint blue light is greater than the maximum kinetic energy of the electrons ejected by the bright red light. With reference to one or more suitable formulae explain why this happens? (3) 10.2.4 The faint blue light is replaced by a bright blue light. What effect will this have on the number of photoelectrons emitted from the metal surface (increase, decrease or no effect)? Explain your answer. (3) [15]

[Total: 200]

Kearsney College Physics (Paper 1) Trial Exam August 2011 Page 13 of 13

Question 6.4

Name: Teacher:

Question 7.6

200 180 160 140 120 100 0

Pressure (kPa)